1. Field of the Invention
The present invention relates to a herbicidal composition which contains 3,4-dichloropropionanilide as the main active ingredient. More particularly, this invention relates to a herbicidal composition which is effective against weeds indigenous to paddy fields during their growth periods. It is also related to a simple method of effectively weeding by direct sowing flooded paddy fields.
2. Description of the Prior Art
Heretofore, many herbicidal compounds for use in paddy fields have been proposed and applied in practice. Most of these herbicidal compounds have been pre-emergence herbicides. However, in paddy fields, the germination and growth of the various weeds is still vigorous as the activity of the herbicidal compound decreases after the treatment of the pre-emergent herbicides. Accordingly, it is very difficult to effectively control such weeds by using only a pre-emergent herbicide and the optimum weeding technique is therefore to control all weeds at about the time of germination in the paddy fields.
In the past, certain herbicidal compounds have been proposed for treating weeds during their growth periods. 3,4-dichloropropionanilide (hereinafter referred to as DCPA) has been so used throughout the world and is quite effective because it has not phytotoxicity to rice seedlings. However, DCPA will kill all existing barnyard grasses and young broad-leaf weeks. Unfortunately, it is an important condition to obtain the herbicidal effect of DCPA that it be applied only after surface drainage. It is then necessary to prevent watering for a least 2 - 3 days after the foliage treatment. The herbicidal effect of DCPA is not expected when applied while water is in a paddy field because of the resultant dilution of the active ingredient DCPA. In the application of DCPA, it is therefore indispensable to apply it after surface drainage. However, the operation of surface drainage during the middle period after a transplantation is quite disadvantageous for several reasons: rice culture management requires a substantial amount of labor, the fertilizer component is lost by draining, the time for application is necessarily, limited, and replacement of the irrigation water is required after the treatment. Consequently, a need continues to exist for an improved DCPA herbicide.